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The systems local IPv4 firewall must implement a deny-all, allow-by-exception policy for inbound packets.


Finding ID Version Rule ID IA Controls Severity
V-217933 RHEL-06-000120 SV-217933r505923_rule Medium
In "iptables" the default policy is applied only after all the applicable rules in the table are examined for a match. Setting the default policy to "DROP" implements proper design for a firewall, i.e., any packets which are not explicitly permitted should not be accepted.
Red Hat Enterprise Linux 6 Security Technical Implementation Guide 2020-09-03


Check Text ( C-19414r376814_chk )
Run the following command to ensure the default "INPUT" policy is "DROP":

# iptables -nvL | grep -i input

Chain INPUT (policy DROP 0 packets, 0 bytes)

If the default policy for the INPUT chain is not set to DROP, this is a finding.
Fix Text (F-19412r376815_fix)
To set the default policy to DROP (instead of ACCEPT) for the built-in INPUT chain which processes incoming packets, add or correct the following line in "/etc/sysconfig/iptables":